Subcortical Motor Systems:
Cerebellum & Basal Ganglia
Lecture 21
Motor Loops
Cortex Subcortex Cortex Spinal cord
Cerebellum coordination of movement
Basal Ganglia selection & initiation of voluntary
movements ~
Cerebellum
Nonmotor functions - memory/language Coordination of complex movements Programs ballistic movements
no feedback during execution direction, force, & timing
Motor learning shift from conscious unconscious ~
Cerebellum: Anatomy
Folia & lobules analogous to sulci & gyri
Vermis - along midline output ventromedial pathway
Hemispheres output lateral pathway
Deep cerebellar nuclei analogous to thalamus ~
Motor Loop Through Cerebellum
Lateral cerebellumsimplest circuit
20 million axons Cortex pons & cerebellum
Prefrontal, Motor, PPC Pons & Cerebellum thalamus
VLc - ventrolateral nucleus VLc M1 lateral pathway ~
Prefrontal PPCM1M2
Pons, CerebellumVLc
Distal Limbs
Lateral CerebellarMotor Loop
Cerebellum: Damage
Lesions - loss of motor coordination Dysynergia
no simultaneous movement of jointsserial movement only
Dysmetric movements to wrong coordinates
Alcohol intoxiction depression of cerebellar circuits ~
Basal Ganglia
Caudate nucleus Putamen
Globus Pallidus Substantia Nigra Tegmentum
Control slow movements Using immediate sensory feedback ~
Striatum
StriatumGlobusPallidus
Substantia Nigra
Thalamus
Cross section of Tegmentum
Substantia Nigra
Prefrontal PPCM1M2
BasalGanglia VLo
Distal Limbs
Basal GangliaMotor Loop
Basal Ganglia Movement Disorders
Parkinson’s Disease
1% of population Nigrostriatal pathway
Substantia nigra neurons die Progressive loss
Hypokinesia Rigidity Bradykinesia Akinesia ~
SMA
Putamen
-Globus
Pallidus (GPi)
-
SubstantiaNigra
+
VLo
SubthalamicNucleus
+
Cortex
+X
Parkinson’s Disease+
Parkinson’s Disease: Treatment
Basal Ganglia - Cholinergic Substantia Nigra - Dopaminergic Drug Therapy
L-DOPA Pallidectomy Tissue transplants ~
Huntington’s Disease (Chorea)
Rare onset 30-40s
early as 20s Degeneration of Striatum
Caudate Putamen
GABA & ACh neurons ~
Symptoms
Khoros = dance Uncontrollable, jerky movements Dementia Progressive
eventually fatal ~
SMA
Putamen
-
-
+
VLo
SubthalamicNucleus
+X
Huntington’s Disease
GPiGPe
-
+
Huntington’s Disease: Cause
Genetic disorder Single dominant gene on chromosome 4 HD mutation -
unstable trinucleotide repeat - CAG # of repeats correlated w/ age of onset ~
HD gene huntingtin 3 forms
mutated form binds to protein involved in energy production neuron starves
Excitotoxicity contributes to degeneration glutamate Nitric oxide (NO) Potential treatment:: Inhibit NO synthase ~
Huntington’s Disease: Cause
Hyperkinesia
Excessive movement Ballism
violent, flinging movements Lesions in subthalamus
less inhibition of VLo excitation of SMA ~
SMA
Striatum
- GlobusPallidus
-
+
VLo
SubthalamicNucleus
+
X
Hyperkinesia(e.g. ballism)